Adding 'rel' attribute to <a> tag in iimage editor (7 posts)

Hello everyone! I just wanted to add the rel='lightbox' in every thumbnail that is generated from the iimage editor, so i can use the lightbox image viewer in my blog. I edited the iimage-browser.php adding the rel='lightbox' in the appropriate values, but when i click 'insert into post' button this attribute is lost! Additionaly if i edit the html of the post and put it manually from there, it is not appearing as well! I figured that WordPress has a sort of validation system that removes every other attribute from the 'a' tag and leaves only the 'href' and 'title' ...How can i edit this thing in order to accept the rel attribute?

I use WordPress 1.5.2 with WYSI-Wordpress plugin that adds more functionality to the post categoy ( WYSIWYG editor )...I cant understand why the changes that i make to kses.php dont affect this...Is there a possibility this plugin to override those edits?

I think i have found the error but the tweaks i have to make are way too many..This plugin uses tiny_MCE which firstly doesnt allow the rel attr and secondly its very hard to insert it...Like Rewriting parts of some functions.. :S